This invention relates to the field of nozzles for the application of glue. More particularly, it relates to a unique air pressure nozzle used to apply a discreet amount of glue to papers, envelopes, or similar articles.
The application of glue to surfaces has long been the subject in the particular field of sealing envelopes, cartons, and other types of products. Different types of glue heads and nozzles have been devised in order to make the application of glue to a surface efficient.
In the field which particularly relates to the application of small discreet quantities of glue to a continual supply of envelopes or the like, a problem has been encountered due to the nature of glue itself. The glue tends to coagulate at the nozzle end, clogging the delivery system.
Most of the nozzles or other applicators for applying a discreet amount of glue to a continual stream of paper articles involve either a pumping action by a piston or the continual application of air pressure in order to elongate the stream of glue.
In the first type of application, a contact head containing a ball bearing is used to apply the glue in a start-and-stop fashion. A "poppet head" glue nozzle applies glue under pressure by opening and closing a hole at the end of the nozzle. As the valve lifts, the glue comes out. As the valve is closed, glue stops. The pumping action of a piston often causes the glue to periodically clog the nozzle. This clogging occurs because glue itself is likely to coagulate and stick to a surface due to its nature.
A contact head application can operate efficiently at 8,000 to 8,500 sheets per hour to be glued. In this contact head application, downtime as well as delivery rate are factors which slow down the efficiency of the operation. In the instant device, the glue head is capable of applying glue to 17,000 sheets per hour over an eight hour day. (While the average is 13,000 sheets per hour, the instant application can reach even higher sheets per hour results given the correct conditions.) In an eight hour day, the instant invention can thus apply glue to 104,000 sheets of paper or other articles per day as opposed to 84,000 sheets per day utilizing the contact head system. It an object of this invention to provide a unique air pressure glue nozzle capable of achieving a high number of applications of glue to a continual stream of paper while being virtually trouble-free.
Applying the glue in a continuous fashion, using oblique air pressure jets to arrange the glue in a particular geometric pattern, has proven to be successful but the clogging of the nozzle still occurs.
The clogging of the glue nozzle creates a long downtime problem since the nozzles have to be unclogged or changed. It is another object of this invention to provide an air pressure nozzle which eliminates clogging at the nozzle tip. It is a further object of this invention to provide a unique method for replacing the glue nozzle in a simple and economical fashion.
The instant air pressure glue nozzle will accommodate all types of liquid resin glues, "pressure break" adhesives or "fugitive" glues of latex and its derivatives. These glues, while having distinctive names, all share the trait of forming an adhesive bond with the application of a pressure change. These adhesives also release with pressure, to allow the bond to be broken without harming the surfaces at the point of attachment, dependent upon the substrate to be glued.
Many delivery systems, as noted above, require mechanical means to start and stop glue flow and for timing the rate of glue application. This starting and stopping of the glue flow causes certain glues to set into their latex state, in one case clogging the applicator by its own mechanical design. The introduction of the instant system for applying glue deals with the necessary periodic nature of applying the adhesive to a continual stream of articles to be glued while still allowing a discreet amount of glue to be applied to the article.
Another problem encountered in the field deals with the wide variety of glues available. Different glues have different viscosities. (Viscosity is the measure of the thickness of the glue or other liquid measured in centerpoise (cp).) Water has a viscosity of approximately 24 at 72 degrees Fahrenheit. Whole milk has a viscosity of 250-300. The typical type of glue used in applying glue to a continual number of sheets on a paper folder has an average viscosity of approximately 150. The instant device is capable of applying glue in the manner below specified regardless of the viscosity of the particular glue used. It is a still further object of this invention to provide an air pressure glue nozzle capable of dispensing discreet amounts of glue regardless of the glue's viscosity. Other and further objects of this invention will become apparent upon reading the following Specification.